Principal Investigator

KURATA Kenji Graduate School of Agricultural and Life Sciences, The University of Tokyo, Professor, 大学院・農学生命科学研究科, 教授 (90161736)
TAKAKURA Tadashi Fukuoka International University, College of Digital Media and Communication, Professor, 国際コミュニケーション学部, 教授 (50011929)

1. Summary research for 2001 : Environmental stress can induce changes in physiological and physical conditions of a plant, and these changes influence the dielectric properties of the plant, which can be detected by measuring microwave transmission characteristics (S-parameter, S21) through the plant and its surrounding space. Therefore, experiments were conducted with tomato plants to examine the potential of using measurements of microwave transmission characteristics for real-time and non-contact monitoring of changes in plants caused by environmental stress. In summary, microwave sensing showed potential as a method for monitoring changes in tomato plants due to water stress. The S21 parameter at different microwave frequencies can be used to monitor different stages of water stress. Consistent trends were observed for the relationship between changes in S21 parameter from 1.2GHz to 2.8GHz and changes in stomatal conductance and photosynthetic rate with stress. However, the timing
… More of changes in S21 parameter varied with the individual plants since the physiological parameters were measured on only one representative leaf per plant. The 1.2GHz was the most sensitive to changes in plant water status and could be useful over a wide range of stress. In higher frequencies, the S21 parameter has potential as an indicator of severe state of water stress. Hydroponically grown tomato plants approximately 60 cm in height were used for this research. For detecting stress in other types and sizes of plants, it may be necessary to choose other frequencies, which are more suitable for the particular plants.2. Summary research for 2002 : The physiological accommodation response to the environmental stress of the plant can induce changes in physiological and physical conditions of a plant, and these changes influence the dielectric properties of the plant, which can be detected by measuring microwave complex dielectric properties of plant materials such as leaves, stems. The objective of this research was to detect these responses of plant against water stress nondestructively. The complex dielectric properties of tomato leaves during water stress were measured with an Open-ended coaxial probe from 0.3 to 3GHz, as well as changes in gravimetric moisture, photosynthetic rate, stomatal conductance and water potential which reflect the physiological condition of the plants. Experimental results showed that the complex permittivity (both permittivity and loss factor) of tomato leaves increased during water stress and the greatest correlation between the complex permittivity and the water potential was observed. In order to confirm these phenomenon the complex permittivities of homogenized tomato leaves were measured and showed quite similar tendencies compared with the results from measuring nondestructively. The complex dielectric models, which describe non-stressed and stressed homogenized tomato leaves could be constructed quite accurately with pure water, pulp, glycine, KNO_s from 0.3 to 3.0GHz. Less